Author Topic: AC fan speed control  (Read 8833 times)

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Offline floobydust

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Re: AC fan speed control
« Reply #25 on: July 03, 2017, 06:50:06 pm »
chinese fans are always super fast because copper is expensive- adding turns to give lower speed costs money.
No this is an AC motor. The speed is dependant on the frequency of the supply and slip. Less copper would make it run hotter, not faster.

In the case of a DC motor, the speed can be reduced, without adding any extra copper by using thinner wire, thus enabling more turns with the same amount of copper.

Quote
I bought a $4 eBay 4000W triac/scr phase control module and it works but the fan motor buzzes and is noisy, and the potentiometer makes sparks sometimes. They are cheap but not so safe.
There's nothing inherently dangerous about a thyristor power controller. It's how it's physically designed which makes it safe or a deathtrap. The picture of the one you're using appears to be dangerous. There probably isn't enough creapage and clearance, even if the heat sink and potentiometer were earthed.

Never run the speed controller with a load equal to its full power rating. De-rate decent speed controller modules slightly and cheap ones by a factor of two or more.

Fans are high-slip motors, B-field strength is set by the winding taps. More copper= more turns higher impedance, lower flux and higher slip.
Less copper, runs hotter = perfect chinese design.
 
 


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